In the art of continuous casting of metals such as steel, it is well known to provide for the cutting of a continuously cast strand of metal into billets. Typically, continuous strands of cast metal are produced by pouring the metal in a molten state through the top of an elevated flow-through casting mold and withdrawing the solidifying metal continuously from an opening in the bottom of the mold as an elongated strand which progressively solidifies as it emerges and recedes from the mold. As the strand is withdrawn from the mold, it typically is cooled in a spray chamber, drawn through a curved roller apron to change its direction of travel from vertical to horizontal, and then is passed through a withdrawal mechanism which provides the power to withdraw the strand from the mold and pull it through the roll apron. The withdrawal mechanism also typically straightens the metal strand since the strand is bent into a curved configuration while passing through the roller apron.
The strand commonly is cut into discrete billets without interrupting the longitudinal travel thereof. One established cutting means includes use of an oxyacetylene cutting torch which is mounted on a movable carriage for movement longitudinally with the cast metal strand while being transversed laterally thereacross to cut the strand laterally. The torch typically is mounted for movement in longitudinally synchronous fashion with respect to the metal strand in a manner to produce, in conjunction with the lateral transversing component of the torch motion, a straight crosscut across the metal strand. The individual billets commonly are passed in sequence onto a run-out table equipped with rollers for conveying the billets from the cutting table.
Although prior cutting torches for the cutting of continuously cast metal strands have generally served their intended purposes, they have nevertheless been subject to certain shortcomings. For example, as the torch cuts across a strand, the molten metal from the cut line runs to the bottom of the cut and solidifies on the lower edge of the cut to form a solid lip (commonly called a bead or fash) therealong. Such fash commonly is a mixture of slag, metal and ash which has generally poor adhesion to the billet. Nevertheless, in the prior art, fash removal has been a difficult and tedious chore.
Some prior approaches to fash removal have included directing a stream of oxygen at the lower edge of the hot strand along the cut line to burn off and/or blow away the molten metal and slag before it can accumulate and solidify. The expense of oxygen makes this approach to fash removal or prevention somewhat undesirable. In addition, the removal mechanism is somewhat uncontrolled in that molten material blown away from the cut line may be deposited on flat surfaces of the billet or on portions of the continuous casting apparatus. Other approaches to fash removal have included tedious and inefficient manual grinding or torch cutting of the cut line edge to remove the solidified fash. These and other prior approaches to fash removal have necessitated excessive and unproductive handling of the billets.
Although difficult and inefficient, prior fash removal apparatus and methods have nevertheless been a necessary part of the continuous casting process, because to leave the fash intact on the billet would invite considerable problems in subsequent processing. For example, the fash on a billet may impact on and damage the rolls or other conveying equipment associated with the cutting table, the runout table or on other parts of the continuous casting system. More significantly, in billet rolling operations, the fash may cause cobbles in the rolling mill.